1. Field of the Invention
The present invention relates to a printer that employs a heat-sensitive adhesive sheet, wherein a heat-sensitive adhesive layer, which normally is not adhesive but becomes adhesive when thermally activated, is deposited on one face of a sheet base material, and produces an adhesive label that has desired characters, symbols, numbers or images recorded on the obverse face and adhesive on the reverse face, and relates to a method for producing such an adhesive label.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Patent Laid-Open Publication No. Hei 11-79152, a heat-sensitive adhesive sheet having a heat-sensitive adhesive layer that becomes adhesive when heated has been put to practical use. The heat-sensitive adhesive sheet has several advantages, such as that handling the sheet before it is heated is easy and that no industrial waste is generated because release paper is not required. In order to manifest the adhesive property of the heat-sensitive adhesive layer on the heat-sensitive adhesive sheet, heating the sheet may be performed using a thermal head, one such as is commonly used for a thermal printer. Moreover, when the face of the heat-sensitive adhesive sheet opposite the thermal adhesive layer is a heat-sensitive printing enabled layer, the same type of thermal head can be used both for printing and for heating the thermal adhesive layer.
A printer for producing adhesive labels has been developed whereby desired characters, symbols, numbers or images can be printed on a printing enabled layer of a heat-sensitive adhesive sheet, the heat-sensitive adhesive sheet can be cut into predetermined lengths, and the adhesive property of the heat-sensitive adhesive layer can be manifested so that the thus produced labels can be attached to products to provide, for example, unit prices or product names (see FIG. 5). This printer includes: a printing device 101, for recording desired characters, numbers, symbols and images on a printing enabled layer 100b; a cutting device 102, for cutting a heat-sensitive adhesive sheet 100 into lengths that can serve as labels; a thermal activation device 103, for thermally activating a heat-sensitive adhesive layer 100a to manifest adhesion; and a conveying mechanism, for conveying the heat-sensitive adhesive sheet 10 through the printer. The printing device 101 includes: a heater (a print thermal head 104) used for printing, which contacts and heats the printing enabled layer 100b; and a first conveying unit (a print platen roller 105), which conveys the heat-sensitive adhesive sheet 100. The thermal activation device 103 includes: a heater (a thermal head 106 for thermal activation) used for thermal activation, which contacts and heats the heat-sensitive adhesive layer 100a; and a second conveying unit (a pair 107a of inserted rollers and a platen roller 107b for thermal activation), which conveys the heat-sensitive adhesive sheet 100. Generally, the cutting device 102 is located between the printing device 101 and the thermal activation device 103, and cuts into labels the heat-sensitive adhesive sheet 100 that has been printed.
For this printer, before the cutting device 102 begins to perform the cutting operation, the conveying forward of the heat-sensitive adhesive sheet 100 must be halted for a period of time (e.g., 0.4 seconds) while a movable blade is moved vertically. That is, while the printing device 101 and the second conveying device of the thermal activation device 103 are halted, the cutting device 102 cuts the heat-sensitive adhesive sheet 100. Therefore, when the adhesive label to be produced is longer than the distance from the cut position of the cutting device 102 to the thermal head 106 of the thermal activation device 103, the operation is halted while the heat-sensitive adhesive sheet 100 is held between the thermal head 106 and the platen roller 105 used for thermal activation. As a result, the heat-sensitive adhesive layer for which adhesion has now been manifested adheres to the thermal head 106. Thus, when sheet feeding is resumed after the cutting has been completed and a label has been produced, the heat-sensitive adhesive sheet 100 is not fed smoothly, and a so-called jam occurs, one which in turn causes a conveying failure. Further, heat generated by the thermal head 106 is transmitted to the printing enabled layer 100b, which causes color development.
An adhesive label that is thus produced and discharged from the printer is not appropriate for use because its appearance is not pleasing. Furthermore, when an adhesive label has become firmly adhered to the thermal head 106 of a printer, all the separate operations being performed must be halted and remedial maintenance must be performed. Thus, as described above, the efficiency with which adhesive labels are produced is deteriorated.
Therefore, in Japanese Patent Laid-Open Publication No. 2003-316265, a configuration is disclosed wherein the speeds of a printing device 101 and the conveying unit of a thermal activation device 103 are limited a heat-sensitive adhesive sheet 100 is deflected and assumes a convex shape between a cutting device 102 and the thermal activation device 103; and while the operation of the conveying means is halted, the cutting device 102 begins the cutting of the heat-sensitive adhesive sheet 100 (see FIG. 6). Specifically, a guide floor member 108 is located below and substantially parallel to the path along which the heat-sensitive adhesive sheet 100 is conveyed, and located above this path, respectively arranged at the front end and at the rear end of the guide floor member 108, are a pair of induction guides 109. According to this arrangement, for the portion of the heat-sensitive adhesive sheet 100 nearer the leading edge and along the guide floor member 108 the forward speed is decelerated, or the forward movement is halted, so that the portion of the heat-sensitive adhesive sheet 100 nearer the trailing edge is conveyed faster than the portion nearer the leading edge. In this manner, an extra long portion of the heat-sensitive adhesive sheet 100 is obtained on the guide floor member 108, between the induction guides 109, and is deflected upward, assuming a convex shape between the induction guides 109. As a result, an adhesive label of a desired length can be efficiently produced.
To produce multiple adhesive labels, generally, a roll member 110, around which the heat-sensitive adhesive sheet 100 is wound, is prepared in advance, and as the heat-sensitive adhesive sheet 100 is progressively unwound from the roll member 110, printing, cutting and thermal activation of the heat-sensitive adhesive sheet 100 are performed.
According to the printer described in Japanese Patent Laid-Open Publication No. 2003-316265, a print thermal head 104 for a printing device 101 is located above the path along which the heat-sensitive adhesive sheet 100 is conveyed, and located below this path is a thermal head 106 for a thermal activation device 103. Therefore, the heat-sensitive adhesive sheet 100 is fed with a printing enabled layer 100b facing upward and a heat-sensitive adhesive layer 100a facing downward. In this case, as shown in FIG. 6, when the heat-sensitive adhesive sheet 100 is wound around the roll member 110 with the printing enabled layer 100b outside and the heat-sensitive adhesive layer 100a inside, the winding direction of the roll member 110 matches the direction in which the heat-sensitive adhesive sheet 100 is to be deflected between the cutting device 102 and the activation device 103. Thus, the heat-sensitive adhesive sheet 100 can be smoothly deflected, and conveying and cutting of the sheet can be smoothly performed.
However, the printing enabled layer 100b is the surface on which characters, symbols, numbers or images are represented when an adhesive label is completed, and on this surface, smudging is not desirable. Furthermore, there is a case wherein when the roll member 110 is formed the heat-sensitive adhesive sheet 100 is wound with the printing enabled layer 100b inside. In this case, as shown in FIG. 7, since the direction in which the roll member 110 is wound is the reverse of the direction in which the heat-sensitive adhesive sheet 100 is to be deflected, the heat-sensitive adhesive sheet 100 can not be smoothly deflected and appropriately cut to desired lengths, and smooth sheet feeding may not be performed. As a result, adhesive labels of the desired lengths can not be produced, the manufacturing accuracy is very low, and deterioration of the production yield occurs.